Method for inserting tendons into sheathing

ABSTRACT

A reinforcing tendon is inserted axially into an elongated passage formed in concrete, soil or rock, by gripping the tendon externally of the passage with a hydraulically operated clamp and moving the clamp towards the passage by means of a pair of hydraulic rams so that the tendon is pushed in its longitudinal direction into the passage. The tendon is fully inserted in a series of steps governed by the strokes of the hydraulic rams. At the conclusion of each stroke, the clamp is released from the tendon and returned along the tendon away from the passage to its starting position where it is ready to again grip the tendon and be moved by the rams towards the passage in the next stroke of the rams to further insert the tendon in the passage. To anchor the rams during their return stroke returning the clamp to its starting position, a second clamp is provided adjacent the mouth of the passage; one of the ends of the rams being connected to the second clamp to be anchored relative to the tendon when the second clamp grips the tendon. Any suitable control system may be provided for automatically operating the clamps and the rams in the proper sequence.

United States Patent [191 Friedrich Jan. 15, 1974 METHOD FOR INSERTING TENDONS INTO SHEATHING [75] inventor: Rene Friedrich, Saratoga, Calif.

[73] Assignee: VSL Corporation, Los Gatos, Calif.

[22] Filed: Dec. 15, 1971 [21] Appl. N0.: 208,129

Primary ExaminerOthell M. Simpson Assistant Examiner-Robert C. Watson Attorney-Browne, Beveridge, Degrandi & Kline [57] ABSTRACT A reinforcing tendon is inserted axially into an elongated passage formed in concrete, soil or rock, by gripping the tendon externally of the passage with a hydraulically operated clamp and moving the clamp towards the passage by means of a pair of hydraulic rams so that the tendon is pushed in its longitudinal direction into the passage. The tendon is fully inserted in a series of steps governed by the strokes of the hydraulic rams. At the conclusion of each stroke, the clamp is released from the tendon and returned along the tendon away from the passage to its starting position where it is ready to again grip the tendon and be moved by the rams towards the passage in the next stroke of the rams to further insert the tendon in the passage. To anchor the rams during their return stroke returning the clamp to its starting position, a second clamp is provided adjacent the mouth of the passage; one of the ends of the rams being connected to the second clamp to be anchored relative to the tendon when the second clamp grips the tendon. Any suitable control system may be provided for automatically operating the clamps and the rams in the proper sequence.

1 Claim, 4 Drawing Figures P'ATENTEDJAN 1 5w 3185.6 1 "r sum 1 or 2 INVENTOR RENE FRIEDRICH ATTORNEYS PATENTEDJANIISIQYA ISHEETZBFZ ATTORNEYS METHOD FOR INSERTING TENDONS INTO SHEATIIING BACKGROUND OF INVENTION Currently, many concrete structures and underground excavations are reinforced or stabilized by imparting to them external forces provided by highly stressed steel tendons. With concrete structures, empty sheaths are customarily placed in the form work prior to concrete pour and with excavations, holes are drilled into the rock or soil. Subsequently, steel tendons composed of bundled strands, wires or bars are inserted into these sheaths or holes, equipped with anchorages and then stressed. Ordinarily, these tendons are pulled into the hole with a winch line.

While the aforementioned conventional techniques are satisfactory when applied to tendons which are relatively light or which do not have to undergo an exceedingly curved path during insertion, they have been found to be unsatisfactory and in some cases inoperable where the tendons are either very heavy or susceptible to large friction losses due to the curvature of the tendons path of movement during insertion.

OBJECTS OF THE PRESENT INVENTION It is therefore an object of the present invention to provide a novel and improved method and apparatus for effectively inserting tendons into sheaths or passages in rock, concrete, soil, etc., and which overcome the aforementioned deficiencies of conventional techniques. Included herein is a provision of such a method and apparatus which may be employed to insert a tendon within a sheath or hole in rock, concrete or soil, etc. regardless of the size or weight of the tendon and the curvature of its path during insertion.

A further object of the present invention is to provide such a method and apparatus which may be employed to control the descent of a tendon into a vertical sheath or hole in rock, concrete or soil, etc. Included herein I is a provision of such a method and apparatus which may be employed to insert a rock anchor tendon into an upwardly sloping hole in rock such as in the roof of a mine or cavern; an otherwise difficult task.

Yet another object of the present invention is to provide such a method and apparatus which in the case of inserting a tendon into a sheath open at both ends, may be employed in conjunction with a conventional winch pulling line acting at the leading end of the tendon.

A still further object of the present invention is to provide such a method and apparatus for inserting tendons which may be operated automatically through a control system.

SUMMARY OF INVENTION In summary, the above and other objects are achieved by gripping a tendon with a clamp device operated by a motor, preferably a hydraulic motor. The clamp device is then actuated towards the passage in which the tendon is to be inserted to thus move, by pushing, the tendon along its longitudinal dimension to insert it axially into the passage. The clamp device is actuated by a motor mechanism preferably one or more reciprocable hydraulic rams connected at one end to the clamp device. At the end of the stroke of the rams, the clamp device is released from the tendon for return in a reverse direction to a starting position for the next insertion stroke of the rams. For this reason. the other ends of the rams are connected to a second hydraulically operated clamp device used to grip the tendon adjacent the mouth of the passage to anchor the rams relative thereto to allow the rams to be actuated in said reverse direction for returning the first clamp device to its starting position ready for the next insertion stroke of the rams.

In one embodiment, the second clamp device is mounted to a bearing plate embedded in a body of rock, soil, concrete, etc. about the mouth of the passage in which the tendon is to be inserted. A suitable hydraulic control system is provided for operating the first and second clamp devices and the hydraulic rams in proper sequence.

DRAWINGS Other objects and advantages of the present invention will become apparent from the following more detailed description taken in conjunction with the drawings in which:

FIG. 1 is a longitudinal cross-sectional view illustrating apparatus for inserting tendons into sheathing in accordance with the present invention;

FIG. 2 is a cross-sectional view taken generally along lines 22 of FIG. 1;

FIG. 3 is a plan view of the apparatus shown in FIG. l; and

FIG. 4 is a schematic view ofa control system for operating the apparatus.

DETAILED DESCRIPTION Referring to the drawings in detail, there is shown for illustrative purposes only a concrete body 10 including an elongated cylindrical sheath 12 into which a tendon 14 is to be inserted in accordance with the present invention for purposes of reinforcing or stabilizing the concrete body. Although not specifically illustrated, it will be appreciated that the invention is applicable to inserting tendons or other elongated reinforcing members into passages which may be formed by excavation in rock, soil or other structures.

Returning to the specific embodiment illustrated, sheath 12 is placed in the concrete form prior to pouring the body 10 in any conventional manner and therefore need not be described, it being understood that the latter forms no part of the present invention. About the mouth of sheath 12, there is embedded in body 10, a bearing plate 16 having anchoring tongs l8. Bearing plate 16 per se is a conventional item, having an aperture 20 therethrough aligned with the sheathing passage for receiving tendon 14.

Apparatus embodying the present invention includes a first clamp device generally designated 22 for gripping tendon 14 circumferentially thereof at a station spaced from the mouth of the sheath as illustrated in the drawings. Clamp device 22 in the shown embodiment includes a rigid support body 24 made from suitable material such as steel for example, and having a central aperture 26 receiving tendon 14. Mounted in support body 24 for movement into and out of circumferential engagement with tendon 14 is a pair of arcuate generally C-shaped gripping members 28 located in diametrically opposed interrelationship. The latter mounting is achieved by suitably shaped passages 29 formed in support body 24 of the clamping device for receiving gripping members 28.

Actuation of gripping members 28 radially in the clamp device body 24 into and out of engagement with tendon 14 is achieved by motors, preferably hydraulic motors 30 respectively associated with gripping members 28. Motors 30 are mounted in clamp device body 24 by means of suitable radial passages 32 formed in the latter. Motors 30 each have an actuating plunger 34 suitably connected to the associated gripping member 28 centrally of the latter to actuate the same upon energization of the motor.

In use, after clamping members 28 are actuated into engagement with tendon l4, clamp device 22 may then be moved toward the sheath for advancing the tendon in its longitudinal direction for axial insertion into the sheath l2. Actuation of clamp device 22 is achieved by another motorized mechanism, preferably one or more reciprocable hydraulic rams 36; there being two such rams 36 illustrated in the drawings. Rams 36 may be conventional double-acting rams including a housing 37 having an elongated chamber or piston passage slidably receiving a double-acting piston 38. In the specific form shown, housings 37 of rams 36 are fixed in any suitable manner to diametrically opposed locations on the face of support body 24 of clamping device 22 with the rams extending in parallel along opposite sides of tendon 14. With the pistons 38 of the rams anchored against movement as will be described, it will be seen that supply of motive fluid into the right-hand end of the piston chamber will cause ram housings 37 to move to the right for advancing the tendon into the sheath. At the conclusion of the latter stroke of the rams, clamping device 22 is operated to release gripping members 28 from the tendon at which time the motive fluid is supplied to the other end of the piston chambers to extend the ram housings for returning clamp device 26 to its initial position ready for the next insertion stroke.

Anchoring of the ram pistons 38 is achieved by a second clamp device generally designated 40 including a rigid support body 42 fixed against the face of bearing plate 16 by means of bolts 44 and having a central aperture axially receiving tendon 14 as illustrated. Clamp device 40 includes a pair of gripping members 46 similar to gripping members 28 of clamp device 22. Clamp device body 42 is formed with suitable passages for receiving its gripping members 46 for movement into and out of circumferential engagement with tendon 14 in the same manner as gripping members 28. Operation of gripping members 46 is also achieved in the same manner by means of hydraulic motors 48 respectively associated with the gripping members 46. The outer ends of the pistons are suitable fixed in any suitable manner to the support body 42 of clamp device 40.

During the insertion stroke of the rams 36 functioning to move clamp device 22 towards the sheath for inserting the tendon 14 therein, the second clamp device 40 is released from the tendon to permit the tendon to be inserted axially into the sheath. At the conclusion of the insertion stroke however, the second clamp device 40 is operated to cause its gripping members 46 to grip the tendon. The first clamp device 22 is then operated to release its gripping members 28 from the tendon whereupon rams 36 may then be operated to extend the ram housings for returning the first clamp device 22 to its starting position for the next insertion stroke. At that time, the second clamp device 40 is released from the tendon to permit the latter to be further inserted upon re-gripping thereof by the first clamping device 22 and actuation of rams 36.

Any suitable control system may be provided for operating the clamp devices and rams in proper timed sequence, one such control system being schematically illustrated in FIG. 4 The illustrated system includes a first control valve mechanism V for controlling the supply and exhausting of hydraulic or other motive fluid relative to the hydraulic rams 36; and a second control valve mechanism V for controlling the supply of motive fluid to clamp device motors 30 and 48. A suitable source of motive fluid is indicated at S while a timing device T is operatively connected to the actuators of control valves V, and V to operate the same in proper sequence. With this system, the tendon may be inserted in a series of strokes each one being governed by one cycle of the system wherein the clamp device 22 is first operated to grip the tendon, the rams 36 are then actuated to advance clamp device 22 towards the mouth of the sheath for inserting the tendon, the second clamp device 40 is then operated to grip the tendon, the first clamp device 22 is operated to release the tendon, and rams 36 are again actuated to return the first clamp device 22 to the starting position ready for the next cycle.

What is claimed is:

l. A method of inserting an elongated reinforcing tendon into an elongated passage in a concrete structure or underground excavation of rock, soil or concrete comprising:

gripping said reinforcing tendon by a clamp device mounted on an anchor member fixed on the body around the mouth of said passage externally of said passage;

pushing said reinforcing tendon in its longitudinal direction into said passage in the axial direction of said passage by moving said clamp device towards said passage by means of a hydraulic ram;

inserting said reinforcing tendon in said passage in a series of steps governed by forward and return strokes of said ram, wherein during the return stroke of said ram, a second clamp device mounted on said anchor member is employed to secure one end of the ram relative to the tendon while said first clamp device is released from said tendon and returned to a starting position by means of said ram, and

including the step of utilizing an automatic hydraulic control system for automatically in sequence actuating the second clamp device to release it from the tendon and actuating the first clamp device to engage the tendon, and then actuating the hydraulic ram to move the first clamp device relative to the second clamp device for inserting the tendon in the passage, and then releasing the first clamp device from the tendon and actuating the second clamp device to engage and grip the tendon, and then acutating the ram for moving the first clamp device away from the second clamp device to its starting position and then repeating the aforementioned sequence of steps. 

1. A method of inserting an elongated reinforcing tendon into an elongated passage in a concrete structure or underground excavation of rock, soil or concrete comprising: gripping said reinforcing tendon by a clamp device mounted on an anchor member fixed on the body around the mouth of said passage externally of said passage; pushing said reinforcing tendon in its longitudinal direction into said passage in the axial direction of said passage by moving said clamp device towards said passage by means of a hydraulic ram; inserting said reinforcing tendon in said passage in a series of steps governed by forward and return strokes of said ram, wherein during the return stroke of said ram, a second clamp device mounted on said anchor member is employed to secure one end of the ram relative to the tendon while said first clamp device is released from said tendon and returned to a starting position by means of said ram, and including the step of utilizing an automatic hydraulic control system for automatically in sequence actuating the second clamp device to release it from the tendon and actuating the first clamp device to engage the tendon, and then actuating the hydraulic ram to move the first clamp device relative to the second clamp device for inserting the tendon in the passage, and then releasing the first clamp device from the tendon and actuating the second clamp device to engage and grip the tendon, and then actuating the ram for moving the first clamp device away from the second clamp device to its starting position and then repeating the aforementioned sequence of steps. 